1. Field of the Invention
This invention relates to a barrier, in particular for damming a tidal waterway during storm tides.
2. Background Information
Barriers for storm tides are structures in tidal waterways with gates which are generally open. On one hand, such a configuration allows a substantially unrestricted flow of tide waves in both directions, and, on the other hand, such a configuration generally does not interfere with the passage of ships. The following requirements, among others, are generally placed by ocean-going shipping on the passage openings in tidal barriers:
On one hand, a ship channel at least 200 to 400 m wide and approximately 12 to 15 m deep at average low water should generally in no way be restricted by the structure. On the other hand, the overall cross section of the waterway should generally be changed as little as possible, to prevent any adverse effects on tidal flow.
It is known that, to meet these requirements, it is possible to use gates which rest on the bottom of the waterway. Furthermore, such gates may be raised by a hydraulic system or by the injection of compressed air. However, such gates may have the disadvantage that all the moving parts are constantly under water, making maintenance difficult. In addition to problems related to filling with sand, silt and deposits, major design problems must generally be overcome for gate heights of more than 20 m.
Also known are hose-type elastic structures disposed on the bottom of a waterway, which may form a barrier body when filled with water, and floatable gate bodies, which are usually supported on a bottom sill by being flooded and submerged. Both of these types of structures also tend to be unsafe under the worst imaginable conditions, or else may be difficult to control on account of their size.
The above-mentioned requirement for maintaining a wide ship channel also tends to rule out all structures in which the forces from the water pressure must be supported by lateral buttresses or supports, because the stability of the structures under load cannot generally be guaranteed. Therefore, the only designs which are usually suitable are those in which the forces exerted, such as by water pressure, may be transmitted directly to the foundation structure and into the river bottom. Such designs include, for example, sliding gates which can be moved on foundations, on a horizontal rail, out of dock-like chambers.
Such a sliding gate, having a triangular cross section, is disclosed in Federal Republic of Germany Patent No. 729 333, as, for example, a sliding gate for locks. Since the sliding gate moves horizontally, it should generally have, for the purpose of horizontal movement, a chamber which can hold the full length of the gate to be moved, in order to free up the entire width of the flow of the waterway. Such a structure tends to require a high construction expense, with consequent high costs. And on account of the rectangular gate surface, the entire flow profile is generally necessarily changed, and, consequently, the velocity of the current is usually increased. That, in turn, tends to have a negative impact on the expense with which the sill and the rails are kept clear, because constant impacts can be expected on account of the high flow velocity.